Preliminary experiments have demonstrated that protein synthesis, assessed by incorporation into protein of labelled amino acids, proceeds briskly and quite constantly in isolated retina for up to 7 hours in vitro. Measurements of rates of synthesis have proved to be sufficiently reproducible to demonstrate relatively small effects due to changes in the composition of the incubation medium, and it is anticipated that response to experimental variables can be measured with even greater precision by the use of double labelling techniques. We propose to use this experimental system to study the relationship between protein synthesis and function in nervous tissue. In some experiments, variables expected to alter function (photic stimulation, neurotransmitters, etc.) will be introduced and the effect determined on protein synthesis, including subcellular sites and types of protein involved. In others, protein metabolism will be altered (e.g., with puromycin) and the effect on function determined by electrical recordings.